Question

Find the value of x.

Answer 1

x = 20°

Explanation:

(4x-10)+x=90

4x-10+x=90

4x+x-10=90

5x-10=90

5x=100

x=20

Answer 2

20

Explanation:

Straight line angles:

Angles on a straight line add up to 180°.

90 + 4x - 10 + x = 180

90 - 10 + 4x + x = 180

Combine like terms.

80 + 5x = 180

Subtract 80 from both sides,

5x = 180 - 80

5x = 100

Divide both sides by 5

x = 100 ÷ 5

`\sf \boxed{x = 20^\circ}`